The isolation and chemistry of niobium and tantalum dimethylamides containing mono- and di-aryloxide ancillary ligands
作者:Scott W. Schweiger、Dana L. Tillison、Matt G. Thorn、Phillip E. Fanwick、Ian P. Rothwell
DOI:10.1039/b101723n
日期:——
The salt complex [Me2NH2][Ta(NMe2)2Cl4] 4 has been isolated from the reaction of [Ta2Cl10] with Me2NH and the anion shown to contain mutually cis-dimethylamido ligands. 4 reacts with Me2NH and pyridine to produce the neutral adducts mer,cis-[Ta(NMe2)2Cl3(HNMe2)] 1 (known compound) and [Ta(NMe2)2Cl3(py)] 5. The solid state structure of [Ta(NMe2)2Cl3(py-4Ph)] 7 shows a mer,cis arrangement of Cl and NMe2 groups. The addition of 2,3,5,6-tetraphenyl- or 2,6-di-isopropyl-phenol (2 equiv) to solutions of 1 in benzene was found to produce a mixture of two isomers each containing a residual Ta–NMe2 and Ta–NHMe2 group. These were formulated as [Ta(OAr)2Cl2(NMe2)(NHMe2)] with the coordinated amine trans to the Ta–NMe2 group and aryloxide ligands either mutually cis or trans. The cis isomer was found to thermally convert to the trans form. The trans isomers [M(OAr)2Cl2(NMe2)(NHMe2)] (M = Ta, OAr = 2,3,5,6-tetraphenyl- or 2,6-di-isopropyl-phenoxide; M = Nb, OAr = 2,3,5,6-tetraphenylphenoxide) are obtained in high yield by treatment of the corresponding tri(chlorides) [M(OAr)2Cl3] with excess Me2NH. The isomorphous/isostructural compounds [M(OC6HPh4-2,3,5,6)2Cl2(NMe2)(py)] (M = Nb, Ta) were structurally characterized and shown to contain the pyridine ligand trans to the Ta–NMe2 group with mutually trans aryloxides. Addition of 2,2′-methylenebis(6-phenylphenol) (HOC6H3Ph)2CH2} to 1 resulted in formation of the compound [Ta(OC6H3Ph)2CH2}Cl2(NMe2)(HNMe2)] 15. The solid state structure of 15 shows the nitrogen atoms to be mutually trans with cis aryloxide oxygen atoms. The eight-membered dioxametallacycle ring is puckered with the methylene bridge folded up towards the Ta–NMe2 group. The reaction pathways leading to these products are discussed.
盐复合物[Me2NH2][Ta(NMe2)2Cl4] 4是通过[Ta2Cl10]与Me2NH反应获得的,阴离子显示出含有互为顺式的二甲基氨基配体。4与Me2NH和吡啶反应生成中性加合物mer,cis-[Ta(NMe2)2Cl3(HNMe2)] 1(已知化合物)和[Ta(NMe2)2Cl3(py)] 5。[Ta(NMe2)2Cl3(py-4Ph)] 7的固态结构显示Cl和NMe2基团呈现mer,cis排列。向1的苯溶液中添加2,3,5,6-四苯基或2,6-二异丙基苯酚(2当量)会生成两种异构体的混合物,每种异构体都包含残余的Ta–NMe2和Ta–NHMe2基团。这些化合物被表征为[Ta(OAr)2Cl2(NMe2)(NHMe2)],其中配位的胺基与Ta–NMe2基团呈反式排列,芳氧配体则是互为顺式或反式。发现cis异构体能够热转化为trans形式。通过用过量的Me2NH处理相应的三氯化物[M(OAr)2Cl3],可以高产率得到反式异构体[M(OAr)2Cl2(NMe2)(NHMe2)](M=Ta,OAr=2,3,5,6-四苯基-或2,6-二异丙基苯氧化物;M=Nb,OAr=2,3,5,6-四苯基苯氧化物)。同构/同构结构化合物[M(OC6HPh4-2,3,5,6)2Cl2(NMe2)(py)](M=Nb,Ta)经过结构表征,显示吡啶配体与Ta–NMe2基团呈反式排列,芳氧配体互为反式。将2,2′-亚甲基双(6-苯基酚)(HOC6H3Ph)2CH2}添加到1中,最终形成化合物[Ta(OC6H3Ph)2CH2}Cl2(NMe2)(HNMe2)] 15。15的固态结构显示氮原子互为反式,而顺式芳氧的氧原子互为顺式。八元的二氧金属环呈现皱缩,亚甲基桥折叠向Ta–NMe2基团。讨论了通向这些产物的反应路径。